1. Field
The present disclosure is directed to additive compositions and lubricating oils containing amide alcohols. In particular, the present disclosure is directed to additive compositions and lubricating oil containing amide alcohols as friction modifiers for reducing one or both of thin film friction and boundary layer friction.
2. Description of the Related Technology
To ensure smooth operation of engines, engine oils play an important role in lubricating a variety of sliding parts in the engine, for example, piston rings/cylinder liners, bearings of crankshafts and connecting rods, valve mechanisms including cams and valve lifters, and the like. Engine oils may also play a role in cooling the inside of an engine and dispersing combustion products. Further possible functions of engine oils may include preventing or reducing rust and corrosion.
The principle consideration for engine oils is to prevent wear and seizure of parts in the engine. Lubricated engine parts are mostly in a state of fluid lubrication, but valve systems and top and bottom dead centers of pistons are likely to be in a state of boundary lubrication. The friction between these parts in the engine may cause significant energy losses to thereby reduce fuel efficiency. Many types of friction modifiers have been used in engine oils to decrease frictional energy losses.
Improved fuel efficiency may be achieved when friction between engine parts is reduced. Thin-film friction is the friction generated by a fluid, such as a lubricant, moving between two surfaces, when the distance between the two surfaces is very small. It is known that some additives normally present in engine oils form films of different thicknesses, which can have an effect on thin-film friction. Some additives, such as zinc dialkyl dithiophosphate (ZDDP) are known to increase thin-film friction. Though such additives may be required for other reasons such as to protect engine parts, the increase in thin-film friction caused by such additives can be detrimental.
Reducing boundary layer friction in engines may also enhance fuel efficiency. The motion of contacting surfaces in an engine may be retarded by boundary layer friction. Non-nitrogen-containing, nitrogen-containing, and molybdenum-containing friction modifiers are sometimes used to reduce boundary layer friction.
U.S. Pat. No. 6,312,481 discloses a monoamide-containing polyether alcohol compounds as additives in fuel compositions that has the formula:
where R1, R2 and R3 are each independently selected from hydrogen, hydrocarbyl of 1 to 100 carbon atoms, substituted hydrocarbyl of 1 to 100 carbon atoms and polyoxyalkylene alcohol of 2 to 200 carbon atoms or R2 and R3 taken together form a heterocyclic group of 2 to 100 carbon atoms or a substituted heterocyclic group of 2 to 100 carbon atoms with the proviso that at least one of R1, R2 or R3 must be polyoxyalkylene alcohol. When one or more of R1, R2 or R3 are polyoxyalkylene alcohol, they are preferably independently selected from polyoxyalkylene alcohol of formula:
where x is from 1 to 50 and each R4 is independently selected from the group consisting of hydrocarbyl of 2 to 100 carbon atoms and substituted hydrocarbyl of 2 to 100 carbon atoms.
U.S. Pat. No. 4,512,903 discloses a lubricant composition containing one or more amides represented by the formula:
where R is a saturated or unsaturated aliphatic based hydrocarbyl radical of about 10 to about 30 carbon atoms; R′ is hydrogen, R or an alkyl group having about 1 to about 30 carbon atoms in a chain which can be straight or branched; R″ is a divalent hydrocarbyl radical including alkylene, alkenylene or alkynylene having 1 to 10 carbon atoms; and n is an integer from 1 to 10. The lubricant composition may be used for products such as diesel engine oils, automatic transmission fluid, turbine oils, aircraft and jet engine oils, outboard motor and other 2-cycle engine oils, gas engine oils, etc. Other components including detergents, dispersants, corrosion and oxidation inhibitors, antifoam agents may also be added to the lubricant composition.
U.S. Pat. No. 4,741,848 discloses a lubricant composition that may be used as a crankcase lubricating oil for internal combustion engines. The lubricant composition comprises a borated compound represented by the formula:
wherein R is a divalent hydrocarbyl group, X is —NR′R″, wherein R′ is a hydrocarbyl group and R″ is hydrogen or a hydrocarbyl group, Y is —OH or X, m is 1 or 2, and n is an integer from 1 to 10 provided that only one free hydroxyl group is attached per carbon atom of the hydrocarbyl group R. The lubricant composition may further include additives such as detergents and dispersants of the ash-producing or ashless type, corrosion- and oxidation-inhibiting agents, pour point depressing agents, extreme pressure agents, antiwear agents, color stabilizers and anti-foam agents.
U.S. Pat. No. 4,334,073 discloses a process for preparation of an amide of the formula:
wherein R1 represent hydrogen or alkyl; R2 and R3 are identical or different and each represents hydrogen or alkyl, alkenyl, alkynyl, aralkyl, cycloalkyl or aryl, in each case optionally substituted, or a nitrogen-containing heterocyclic radical.
In recent years there has been a growing desire to employ lubricating oils to provide higher energy-efficiency, especially lubricating oils that reduce friction. The present disclosure provides improved lubricating oils that may reduce one or both of thin film friction and boundary layer friction.